The Most Important Manure With Nitrogen

Manure can be the key to high crop yields.

Nitrogen-rich manure is a classic tool for promoting healthy plant growth. The nitrogen content in the waste of different animals varies, which in turn determines how much you need to add to your garden. Each 100 square feet of garden benefits from between 25 to 100 pounds of composted manure. If your manure source is one of the lowest in nitrogen content, use more of the material -- especially if you haven't fertilized the garden in the last year or two. If the manure is rich in nitrogen, you'll be able to get away with using less. Never add dog, cat or human waste to your garden beds, because they contain harmful bacteria, even when composted.

Dry Manure

Aged manure is that which has been allowed to dry and decompose. It is also known as composted manure or dry manure. Dried bat "guano," as it is known, has the highest percentage of nitrogen of commonly used aged manures -- bat waste is made up of 10 percent nitrogen. Other high-nitrogen manures sources are those of sheep, pigs and poultry, which each contain between 3.2 and 3.5 percent nitrogen. Rabbit and horse waste are each about 2.3 percent nitrogen. Lowest among the common forms of aged manures are those of goats and sheep, which are made up of between 1.3 and 1.7 percent nitrogen.

Fresh Manure Drawbacks

The fresh manure of broiler hens is made up of about 3 percent nitrogen, while the waste of other animals contains between 0.7 and 1 percent nitrogen. But fresh manure, while being less nitrogen-rich than aged manure, is also a bad choice to apply to your current garden for other reasons. It is heavier and harder to transport and can transfer weed seeds and potentially harmful pathogens to your garden soil.

Considerations

Nitrogen content is only one aspect of choosing manure. If you raise your own animals or have access to high-quality manure, this free nitrogen source is likely to be a more practical resource than expensive mail-order bat guano. If you do use local manure, age it for at least two months before adding it to a current garden. Alternatively, work fresh manure into your soil and wait at least two months before planting. Cover the amended soil with hay or grass clippings to lessen the amount of nitrogen that is leeched out of the soil.

Additional Nitrogen Sources

Other organic forms of high-nitrogen fertilizers exist. Blood meal contains up to 14 percent nitrogen, while feather meal contains 12 percent nitrogen and fish meal 10 percent. If you're seeking plant-based nitrogen sources, look for cottonseed or soybean meal, which both are made up of 6 to 7 percent nitrogen. You may also get good results by growing "green" manures -- cover crops such as clover, sowing it several months before you plant the main garden. The roots of these cover crops fix nitrogen from the air into the soil, once the cover crops are pulled up and tilled back into the garden.